What is the edge length of a face-centered cubic unit cell made up of atoms having a radius of 175 pm

495 pm (see the relationship between the edge length (a) and radius (r) of atoms in attachment).

Explanation:

A crystalline solid possess rigid and long-range order; its atoms, molecules, or ions occupy specific positions. A unit cell is the basic repeating structural unit of a crystalline solid. Each sphere in the unit cell represents an atom, ion, or molecule and is called a lattice point. The way the spheres are arranged in layers determines what type of unit cell we have.

In the face-centered cubic cell, there are spheres at the center of each of the six faces of the cube, in addition to the eight corner spheres (see the second picture in the attachment). Each sphere in this arrangement is said to have a coordination number of 12 since each sphere is in contact with six spheres in its own layer, three spheres in the layer above, and three spheres in the layer below. The coordination number is defined as the number of atoms (or ions) surrounding an atom (or ion) in a crystal lattice.

In the first picture in the attachment we can see that the relationship between the atomic radius r and the  edge length a face-centered  cubic cell is:

a=√8*r

Therefore, the edge length will be √8*175 pm = 495 pm

i think the answer is terrae but not 100 percent sure. ▓▬▬ §

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.